Background and Aims: Different additives have been used to prolong Brachial plexus block. We evaluated the effect of adding Dexamethasone to Ropivacaine for Ultrasound guided Supraclavicular Brachial plexus blockade. The primary endpoints were the onset and duration of sensory and motor block and duration of analgesia. Materials and Methods: A total of 60 patients (18-60 years) satisfying inclusion and exclusion criteria posted for elective upper limb surgeries under supraclavicular Brachial plexus block were divided into two equal groups (Group R and RD) in a randomized, double-blind fashion. In group RD (n= 30) 30 ml 0.5% Ropivacaine plus 8 mg (2 ml) of Dexamethasone and group R (n = 30) 30 ml 0.5% Ropivacaine plus 2 ml normal saline were administered in Ultrasound guided supraclavicular block. Sensory and motor block onset times and block durations, duration of analgesia, and side effects if any were recorded for each patient. Results: Demographic parameters were comparable in both groups. Onset time of sensory and motor block were shorter in Group RD (10.15 + 1.14 min and 14.95 ± 0.83 min respectively) than in Group R (12.45 + 2.76 min and 16.05 ± 1.96 min respectively) (p = 0.001). Duration of sensory and motor blockade were longer in Group RD (909 ± 22.10 min and 878 ± 19.47 min respectively) than in Group R (450 ± 27.74 min and 420 ± 23.17 min) (p = 0.001). Duration of analgesia was longer in Group RD (1004 ± 25.49 min) than in Group R (498 ± 35.43 min) (p = 0.001). Intra-operative hemodynamic parameters were comparable in both the groups without any adverse effects. Conclusions: Dexamethasone when added to Ropivacaine for Brachial plexus block shortens the onset time and prolongs the duration of the block and the duration of post-operative analgesia.